/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.facebook.presto.execution.scheduler.nodeSelection;

import com.facebook.presto.execution.scheduler.ResettableRandomizedIterator;
import com.facebook.presto.metadata.InternalNode;
import com.facebook.presto.metadata.Split;

import java.util.List;

import static com.facebook.presto.execution.scheduler.NodeScheduler.selectNodes;
import static java.util.Objects.requireNonNull;

public class RandomNodeSelection
        implements NodeSelection
{
    private final int minCandidates;

    private final ResettableRandomizedIterator<InternalNode> randomCandidates;

    public RandomNodeSelection(
            List<InternalNode> eligibleNodes,
            int minCandidates)
    {
        requireNonNull(eligibleNodes, "eligibleNodes is null");
        this.randomCandidates = new ResettableRandomizedIterator<>(eligibleNodes);
        this.minCandidates = minCandidates;
    }

    @Override
    public List<InternalNode> pickNodes(Split split)
    {
        randomCandidates.reset();
        return selectNodes(minCandidates, randomCandidates);
    }
}
